


Instinct - Brat AU (Miscellaneous Story #1)

by Cyan_Sky1



Category: The Amazing World of Gumball
Genre: Anal Sex, BDSM, Collars, Doggy Style, Gay Sex, I’m still working on the story ok sush, M/M, Master/Pet, Mating Cycles/In Heat, Oral Sex, Pet Names, Pet Play, Rob is 19 And Gumball is 18, Rough Sex, The Experiment was my most weirdest smut fic sure, also I’m publishing this the day before my birthday, blowjob, but this fanfic takes the cake of my kinkiest fanfic now, cat play, happy early birthday to me I guess, kitten play, like a bonus smut fic, mentions of BDSM, this is a Miscellaneous story to the actual Brat AU story btw, thus is my first fic for my Brat AU btw
Language: English
Status: Completed
Published: 2018-09-07
Updated: 2018-09-07
Packaged: 2019-07-08 03:24:24
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,912
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15921818
Author URL: https://archiveofourown.org/users/Cyan_Sky1/pseuds/Cyan_Sky1
Summary: Rob notices Gumball is about to go into his monthly heat, and he decides for this month to propose something a little special. He only gives Gumball one rule: Let himself be free, and do whatever his instincts tell him to.





	Instinct - Brat AU (Miscellaneous Story #1)

**Author's Note:**

> Guys this legit makes me pretty damn aroused when I myself read this so I hope it does the same for you lmao, enjoy~

The day started off like any other day, really. Gumball got dressed and now was sitting at the table set next to the kitchen, happily chowing down on an egg sandwich he made while waiting for Rob to wake up and join him to begin the morning together. 

He smiled in between bites of his breakfast as he saw Rob finally exit his room, and walk over to the calander they share to mark important dates. He checks off yesterday on the calendar, then looks like he notices something that was written down on it. The blue cat frowns and tries to squint to see what he is boyfriend is looking at, but his static arm blocks him from seeing. His ears flick to the sound of Rob’s body glitching, and his static grows louder for a second and it darkens a bit in color. Before Gumball could ask anything, the cyclops moves to get a banana and gets the plate of two eggs the blue cat made for him and sets it down on the table. The look on his face tells him he was thinking about something, but he couldn’t decipher what.

“So Gumball,” The cyclops begins to speak after he’s comfortably sitting in his chair across from diss blue cat, “I noticed that according to the calendar your scheduled to start your heat sometime tomorrow.”  
“O-Oh crap really?” Gumball had totally and completely forgotten that his heat was going to start soon, but now that he thinks about it he notices his heart race had picked up a bit, an early sign of his heat beginning soon.  
“Yeah. So I had an idea for this heat cycle....um....i-if you’re up to trying something new I guess.” His static starts to speed up a some more, and he looks down nervously and wrings his hands a bit.  
“I’m listening.” Gumball quirked a brow at Robs unusual nervous behavior, but makes a mental note at how cute it is anyway.  
“Basically um......when you feel any urges or instincts starting tomorrow t-to be a cat-I mean act like a literal cat I mean,” Rob shuts his eye and his face flushed a deep shade of pink, his hair momentarily glitching, “You could um-I mean like uh....you have my full permission to just let yourself be a cat tomorrow, ok? Whatever you want to do while you’re in your heat, whatever urges you get, just let yourself do it. I don’t want you to hold yourself back for this heat cycle.”

Just the fact that he’s asking this makes the blue cat’s dick twitch.

“Are you asking me if I can let myself go feral for my heat tomorrow?”  
“Y-Yes.” The cyclops takes a deep breath and straightens up a bit, trying to assert his dominance back. “Essentially, do you want to be my lil’ kitty cat tomorrow~?”  
“Oh man...” Gumball squirms in his seat, and he feels his cock start to become erect.  
“Are you sure you want me to go feral? I don’t let myself do it at all really....when I do that’s when I start to become a real brat-“  
“-Well I did some research on that actually.” Rob smirked, and it makes the blue cat’s stomach flip, “I read that when cats go into heat they feel better if they let themselves completely be feral, so I figured if I gave you permission to let yourself do that tomorrow it’ll help your heat not be as bad.”  
“O-Oh....” The blue cat swished his tail a little in thought, and after a beat of silence Rob gently speaks up.  
“So....do you wanna do it?” Rob smiles with a certain genuinenity that makes Gumball feel a bit better.

If he was going to let anyone see his feral side, it would be Rob.

“Ok. I’ll do it.” The blue cat smiles, and Rob glitches again and returns the smile, very obviously excited.  
“I promise you you’ll be safe. And you won’t be judged. I just want you to feel better during your heats, and I think this may help you. However the usual safe words will still be in place ok?”  
“Alright. I’m excited for tomorrow then.”

And with that the couple begins eating breakfast again, excited for what tomorrow may bring.

——

Rob woke up the next morning like usual. He got out of bed, he stretched, he glitched into his usual clothing, he took his morning piss, he brushed his teeth. It was completely absent from his mind that his partner wasn’t in the bed, nor was he in the bathroom when he got up. 

So when he went down the hall into the kitchen to get some breakfast, today a bowl of cereal because he didn’t feel like making anything else, you better believe he wasn’t prepared for the sight he saw when he turned around:

Gumball was eating his usual egg sandwich butt naked at the table.

Rob nearly drops his bowl of cereal right then and there.

He feels his dick twitch as it usually does when he sees his boyfriend naked, but he ignores it so he can set his bowl down on the table and sit down across from him in his chair. After he’s settled, he takes a few seconds to stare at Gumball until he finally remembers why he may be shirtless. He told him he can do whatever he needs to do today to help with his heat, and he remembers now that during his research on it he read that some animals that have heats often feel much better if they don’t wear any clothes. Huh, well....if it makes him feel better then he guess he will allow it for the week. 

“So, how are you feeling right now?” Rob tries to start a conversation, but Gumball only gives him a indecipherable look, but then very suddenly scarfs down the rest of his sandwich, swallows it whole, and gets out of his chair to walk on all fours on the floor. Wait-He’s on all fours?! Ok...he may be taking this further the Rob thought he would.

He watches as the blue cat makes his way to the cabinet, and looks up with him with big innocent cat eyes as he begins pawing at the door. Hold on, that’s the cabinet holding all of their extra BDSM supplies that aren’t in their room....along with his.....  
“Oh, you want your bell collar?”  
“Meow~!” 

Oh fuck. He seriously meowed just now. 

But...wait a minute....he isn’t sweating or feverish looking at all, nor is there a clouded hazy look in his eyes.

The little shit was doing this on purpose.

“Alright, if you want to play like that..” The cyclops stood up from his chair, and moved Gumball aside so he can open the cabinet and get the collar himself, “then you will be collared and leashes by me for the day *personally*.” Rob inspects the collar quickly to check if everything on it was intact. The collar was made of black leather, study and thick, but there was a bell with a pink bow glued to the back of said bell. What kept the bell attached to the collar was a silver loop, shaped like a D so it can easily clip a attachable leash but still not be uncomfortable around Gumball’s neck. He gets out the matching leash, black leather sewed with matching pink thread, and kneels down to Gumball’s level to fasten the collar around his neck, making sure it’s adjusted to where it’s tight enough for him to not be able to take it off himself, but not tight enough to where he couldn’t breathe comfortably. He notices while he puts on the collar Gumball sits still for him, which makes him grin. After he’s sure the collar is secure, Rob then clips the leash to the collar before standing up again. Seeing as how Gumball is almost a foot apart from Rob height wise, and now that he’s on all fours, the cyclops practically towered above the blue cat, and the feeling of power over the small thing made Rob’s dick harden a little.

“You’re going to be my pet for today. You’re going to be my little kitten.....actually, that name suits you. My little kitten. Do you like that?”  
“Meow~!” Gumball nodded his head eagerly as he mewled in delight, his dick getting notably harder from the nickname.  
“Heh. Good. Then I hope you don’t mind walking with me back to the table so I can finish my breakfast?”

—-

As the day passed Rob’s boner only got harder as he watched Gumball act like a cat. He watched as he walked around the house on all fours, stared when he meowed at him to ask for water or some food, but the cyclops finally relaxed when the blue cat fell asleep on the couch purring as his body was curled up in a tiny ball. 

He turned on the TV, watching some hooligans on there try to pull pranks on each other. The goal of the show was to make one of them call out for mercy, but it looks like neither of the contestants are willing to call out the ‘safe word’ that easily. He actually almost became invested in the show to see if the next upcoming prank would actually work, until he heard a sound coming from Gumball. He turns down the volume on the TV and turns his head to look at him, and realize he’s starting to mewl and moan in sleep. 

.....Oh lord his heat is starting now isn’t he?

The cyclops turns off the TV, and turns all of his attention to his boyfriend now. His cheeks become redder and redder, and his fur slowly becomes more and more damp from his sweating. The blue cat’s ears flop down in his sleep, and his breathing appears to become faster and more labored when his chest rises up and down more and more. Rob feels himself tense up, waiting in anticipation for the cat to wake up before realizing he would know he was watching him if the TV stays off, so he turns it back on and turns the volume back up and forces himself to watch the program instead, only allowing himself little glances towards the cat to check if he’s waking up. 

Sure enough, Gumball wakes up, yawning before looking down to realize he does indeed have a boner now, and his heat was finally in full effect. His vision was a bit blurred, and he couldn’t seem to blink away the haziness in his eyes. But he didn’t care. His entire body was aching now, pleading for attention, and as he turned his head around and recognized the familiar figure on the couch, he felt himself completely let go and let his instincts run wild. 

Rob lets himself finally look at Gumball again and oh shit. He’s looking at him now. He can see that tell tale glazed over look in his eyes, indicating that he’s in heat. He turns off the TV again, this time without looking as he can’t seem to tear his eyes away from his boyfriend now. He feels his back straighten up, and his body go a bit numb as it glitches, making a static crackle echo in the now silent room. The cyclops watches with a wide eye as the blue cat slowly but surely saunters forward to him on all fours, his tail swishing back and forth in a hypnotizing manner. 

“Mmmmrow~?” Gumball lets out a drawn out mewl, almost like cats do when they’re trying to get their owners attention. The cyclops almost immediately feels his dick get hard all over again. 

One thing’s for sure. He certainly has his attention now. Rob licks his lips a little bit before glitching out of his shirt and pants, smirking as he decides to play along with Gumball.

“What’s that, Kitten? Do you need something?” The cyclops gave his best suggestive look to him as he went to hold his dick in his hand, feeling himself throb a bit in his hand since he neglected his constant boner practically all day.  
“Meow~!” He responded with a cheerful meow, moving his ears up to make them twitch up. He finally made it right in front of Rob, and the cyclops felt his heart leap to his throat when he saw the blue cat trying to nudge his hand away from his dick.  
“Oh, does my Kitten need his milk~?” Rob snickered at his own terrible pun, but stopped when Gumball moved his hand away from his dick successfully and began to lick it.

While his tongue isn’t as rough as a regular cat, he knows how to still lap like a cat would to drink water. And now he apparently knows how to lap at dicks as well. The cyclops lets out a low moan and closes his eye, lightly petting the top of his Kitten’s head as a small signal to keep going.

Gumball makes sure to keep to his teasing nature more then ever, not allowing himself to use his paws to pick up the dick and finally put it into his mouth because after all, he’s using them to keep himself upright now. He looks up at Rob as he continues to lap at his dick, stopping to kiss his bulge every one in a while. After a couple of minutes the cyclops finally opens his eye to see why he wasn’t putting his dick in his mouth already, only to remember he’s still in cat mode. Of course. He needs his paws right now, right? Rob finally takes the hint and moves his hand over to move his dick upwards, facing right into Gumball’s waiting mouth. He purrs happily, and begins to lap at the tip of his head, making sure to aim directly on his slit. The cyclops moans again, feeling a shiver shoot down his spine. After a few more laps at the tip of his head, Gumball finally takes his dick into his mouth, slowly but surely letting it go all the way down his mouth and into the back of his throat.

But then he just sits there, looking up at Rob some more. Does he want him to move his hand? He moves his hand and put it back on his head, going back to petting him. That seems to be the right thing to do, because he very suddenly began purring and holy shit......

He’s purring around his dick.

The vibrations of the purring sends chill after chill shooting through his body, and Rob nearly doubles over and cums right then and there. He lets out another moan, this time much more intense. He feels it when the blue cat’s throat contracts, and it squeezes him so tightly it almost hurts. Gumball waits until his throat stops contracting, then continues to purr while slowly bobbing his head up and down around Rob’s dick, making the cyclop’s head practically spin. He begins to scratch the blue cat’s back now, making sure to make it a bit tougher then how most people scratch their cats. The rough treatment makes Gumball purr louder, and throat fuck Rob with renewed determination.

Rob throws his head back and moans, he’s super close to cumming now. He feels Gumball slow down his purring right as he moans and looks down to see him looking at him once more, and now he’s pretty eager to make him start back up again and he thrusts his hips into his mouth a bit, trying to chase his much needed orgasm. The thrust seemed to be welcomed by Gumball, and he locks eyes with his boyfriend and smiles around his dick as he purrs as hard and as loudly as he could, curling his tongue around his dick as well. Rob has had it at this point, and finally gives in and grabs the blue cat with both of his hands, fiercely thrusting into his throat. It only took a few thrusts before Rob finally came, and Gumball stopped purring so he could swallow every last bit of cum up. Right after he was done though, the blue cat collapsed and gave out a mewl of distress, and Rob came out of his orgasm daze to check his boyfriend.

“What’s the matter, Kitten? Are you ok?” Rob moved Gumball to where he was laying next to him on the couch instead of sharing the same seat as him, and sees some clear liquid pooling out of Gumball’s ass.

It was in this moment he recalled that a lot of animals in heat, boys mainly, have this thing called slick, which is a natural line that build up in their ass so they can be fucked without any lube. If they don’t let it out and let it build up inside of them it can cause pain sometimes, and it looks like Gumball tried holding his slick in while giving Rob a blowjob.

“Kitten, what did I tell you?” The cyclops frowned, and flopped Gumball over on his stomach. He pulled his ass cheeks open, and sure enough his hole was glistening, nice and wet from the slick that was building up.  
“Don’t hold back on me. If you need to let something out, or if you have an instinct you need to get out of your system, then let it all out. I want to see you letting go for me.” Rob licks his lips, and decided to give the blue cat a reward for giving him a much needed blowjob. The cyclops puts a pink finger inside of the blue cat’s ass, and he meows loudly, and Rob can hear him gasping for breath.  
“Hey, hey, relax. I’m not gonna hurt you little Kitten.” Rob affectionately leans down to kiss Gumball’s lower back then begins scratching it again, causing him to start up his purring once more. A flick of the tail tells him to keep going, and Rob decides to waste no more time.

It’s time to test out this slick of his.

The cyclops aims his cock right at Gumball’s ass, then slowly but surely pushes in. Gumball can feel every single inch as it slowly slides in, and my god is he meowing loudly now. Before the blue cat could even stop himself though his tail reaches over to caress Rob’s chest, and the fur tickles him a little. But he knows damn well what he’s trying to do. As he bottoms out inside of him, Rob moans when Gumball finds the sensitive spot on his torso: his collarbone. He begins to shiver when it gives a teasing circle around the sensitive nerves, and before he knows it he feels a glitch coming on.

“S-Sorry!” He gave out a warning before he lets out a shock, the zap of energy going straight inside Gumball’s ass. He moans loudly, his arms giving out.  
“Shit, I’m so sorry! Are you ok?” Rob waits to get a response from Gumball, careful to not pull his dick out in case that would hurt him more. After a few breaths of air though he gets up on his hands and knees, looks back at Rob, and gives his dick a squeeze with his inner muscles.  
“Meow~?” He’s asking for him to start moving, Rob is sure of it.  
“A-Are you sure?” Gumball nods, and smiles at him. It’s like he’s practically telling him with his eyes ‘I don’t want you to hold back either~’ and that look alone makes the cyclop’s dick throb.  
“Alright, but meow three times for me if it becomes too much ok?” The cat rolled his eyes as if to say ‘oh please I don’t need a safeword I just need to be fucked’ but then smiles and nods again anyway.

Rob takes a breath, then grips Gumball by his hips, giving him leverage. He then slowly pulls out, then very quickly gives a firm thrust back in, a way of testing if the blue cat could handle it. The cyclops hears him let out a small squeak that bottoms out into a moan, so he continues to keep going. As each thrust continues he begins to go into a steady pace, not willing to make the blue cat wait any longer.

“Meow~!” Gumball calls out a loud cat noise, and purrs loudly, the noises sounding like it’s coming straight from his diaphragm, making it loud and almost a pitch lower then his normal voice. His tail begins to twitch, before lunging back to tease Rob’s chest. The cyclops takes it as a sign to keep going, and moans loudly when he feels his collarbone being assaulted again. He grips the blue ass closer to his hips, and only thrusts deeper.

Eventually the collarbone assault along with fucking Gumball gets to him again, and he begins to glitch more, this time not stopping when he feels it go inside the blue cat. The result is almost immediate, as Gumball’s mewls become louder and longer, and now he’s desperately hitting his ass back into Rob’s hips to meet his thrusts.

“Mmn-ah! God, w-who’s my little Kitten~?” Rob leans over, and wraps his arms around his chest, now pressed up against his boyfriend’s back.  
“Meow~!” Gumball calls out in response to the cyclop’s teasing question in between moans. 

With the new angle he was thrusting inside of him in it hits his prostate with a hard strike, and he’s barely able to hold himself upright now. The cyclops is during him insane now, and he fucking knows it. The blue cat’s mewls become more pronounced, and every time he tries to purr again it gets interrupted with a new thrust to his prostate. He tries to ask to cum by meowing, he was so close an Rob knows what to do to make him cum. He needs to be touched, and badly. Trying to get Rob’s attention he looks back, and catches his eye. He wiggles his butt a little before he thrusts back in again, trying to swing his dick towards his direction. Luckily Rob gets the hint.

“Aw, is my kitten close? Does my kitten need to be jerked off to cum?”  
“Meow!” Gumball calls out with a hoarse voice, and something tells Rob that he needs to cum, now. So he gives his little kitten exactly what he begged for, and reached over to jack him off.

It only took two firm strokes before Gumball lost control of himself, cumming long and hard with one last meow drawing itself out from the very bottom of his voice, reaching the very pure instincts urges inside of him and leaving him the most satisfied he has ever been in his entire life.  
Meanwhile Gumball’s ass clenches around Rob’s member hard, practically squeezing the cum out of him too. He feels his inner resistance snap, and he gives one last thrust before giving into his orgasm as well.  
When the boys finally finish, they collapse on the bed together, laying right on top of the cum that Gumball let out. The couple takes a few seconds to bask in the afterglow, before Rob finally speaks up:

“Ok kitten, I know you hate water, but we have to shower now.”  
“Meow!”  
“Sush, we can play some more if you behave.”  
“M-Meow...”  
“Good kitten~”


End file.
